// define the variables
circle_in_radius=7;
circle_out_radius=8;
height=12;

spacer_thick=1.8;

intersection(){
    difference(){

    cylinder(h=height,r1=circle_in_radius,r2=circle_out_radius,$fn=100);
    
    cylinder(h=height-spacer_thick,r1=circle_in_radius-spacer_thick,r2=circle_out_radius-spacer_thick,$fn=100);
}

    sphere(sqrt(height*height+circle_in_radius*circle_in_radius),$fn=200);


    
}
